The present invention relates to the percutaneous treatment of aneurysms, and in particular apparatus and methods for balloon assisted occlusion of cerebral aneurysms.
Aneurysms of the cerebral arteries are areas of blood vessel which have been weakened through disease or injury and have subsequently expanded due to the pressure of blood flow.
Cerebral aneurysms are particularly dangerous as thrombus (blood clot) formation can occur within the aneurismal sac, greatly increasing the risk of emboli formation and stroke. In addition, as the vessel is weakened at the aneurysm site, blood vessel rupture is more likely. This condition, if left untreated, quickly results in death.
Traditional treatment of cerebral aneurysm at risk of rupture has been a craniotomy (drilling through the skull) and occlusion using a cerebral clip. This operation carries significant risk and complexity due to its invasive nature. It is also only indicated for a narrow selection of patients due to that risk and because some parts of the cerebral vasculature are simply not accessible through the skull without having to damage the brain.
Cerebral aneurysms fall into two main anatomical variants, which are illustrated in FIGS. 1a to 2b: 1) “saccular aneurysms” 100 (see FIGS. 1a and 1b), which as their name suggests are round sack-like distensions 100 with a narrow opening 102 into the native vessel 104; and 2) “fusiform aneurysms” 200 (see FIGS. 2a and 2b), which are concentric distensions 200 of the blood vessel 104 with less well-defined edges than a saccular aneurysm 100.
In recent years, percutaneous techniques have arisen to treat cerebral aneurysms using wire coils to artificially embolise the distended tissue. FIG. 3a illustrates application of this technique to a saccular aneurysm 100. A catheter 300 is fed up to the aneurysm mouth 102 where a platinum wire 302 is pushed out of the catheter tip 304, into the aneurismal sac 100. This wire 302 then coils into the sac 100, progressively occluding the aneurysm 100. When enough wire 302 is implanted, the clinician can simply disconnect the wire 302, which should stay in place.
This method is well established and has been in use since 1991. However, it is generally only applicable for narrow necked, saccular aneurysms 100 as these shapes lend themselves well to the wire 302 coiling round into a ball.
For wider necked aneurysms 320 (see FIG. 3b), i.e. those which are less saccular and more fusiform, this process may not be possible, as the wire 302 will tend to exit the aneurysm mouth into the native vessel 104. This scenario should be avoided as wire 302 coils in the blood stream may pose a thrombus risk.
FIG. 3b illustrates one approach that clinicians have used to avoid this. A compliant balloon 312 is positioned at the site of interest via a second catheter 314 and used to force the wire 302 round and back into the aneurismal sac 320. On inflation, the balloon 312 conforms to the local vessel anatomy forming a barrier to the coiling wire 302. Such balloons 312 can only be inflated for a maximum of 2 minutes at a time because, when inflated, they occlude blood flow through the vessel 104.
This prior art procedure requires the coil delivery catheter 300 and at least one balloon delivery system to occlude the aneurysm. As separate units, these devices cause significant crowding in an already small vessel 104 and, due to the high compliance of the deployed balloon, there is little scope for manoeuvring to re-adjust the delivery catheter 300 if multiple balloons were to be used.
An object of the present invention is to overcome at least some of the problems associated with the prior art.